Formation of a lithium comprising structure on a substrate by ALD

ABSTRACT

A method for the formation of lithium includes a layer on a substrate using an atomic layer deposition method. The method includes the sequential pulsing of a lithium precursor through a reaction chamber for deposition upon a substrate. Using further oxidizing pulses and or other metal containing precursor pulses, an electrolyte suitable for use in thin film batteries may be manufactured.

RELATED APPLICATIONS

More than one reissue application has been filed for the reissue of U.S.Pat. No. 8,894,723, including the present application, U.S. applicationSer. No. 15/806,846, and U.S. application Ser. No. 15/360,153. Thepresent application is a reissue continuation of U.S. application Ser.No. 15/806,846, filed Nov. 8, 2017, which is a reissue continuation ofU.S. application Ser. No. 15/360,153, filed Nov. 23, 2016, now U.S. Pat.No. RE46,610, which is an application for reissue of U.S. Pat. No.8,894,723 (previously U.S. application Ser. No. 12/810,897), filed Dec.23, 2008 as PCT/NO008/000468, which claims priority to Norwegian PatentApplication No. 20076696, filed Dec. 28, 2007, each of which isincorporated herein by reference in its entirety.

The present invention relates to a method for formation of a lithiumcomprising surface layer on a substrate.

There has in later years been a large emphasis on improving methods forthe formation of thin material layers on substrates of various kinds inorder to produce amongst others electrolytes. It has long been a goal toproduce as thin as possible, as well as defect free layers of Lithiumcomprising materials on a substrate in a controlled fashion. This hasbeen of particular interest for application in battery technology.However the earlier described methods are cumbersome and expensive, andthere is a great need for cheaper and better production methods. ALD(atomic layer deposition, also known as atomic layer chemical vapourdeposition, ALCVD, or atomic layer epitaxy ALE) presents all thenecessary properties for the formation of thin film layers upon asubstrate, however it has been thought that it would not prove possibleto use ALD techniques for compounds only having a single ligand such aslithium. It has been thought that single ligand compounds could notpossibly be deposited using an ALD method, as the single ligand oflithium would react with the surface such that there would be noself-limiting, growth mechanism to prevent further growth according tothe ALD principle. This has empirically been proven to be false as isshown in the present application that describes a method for theformation of thin film lithium-comprising layers on a substrate.

SHORT DESCRIPTION OF THE ALD METHOD

ALD also known as atomic layer chemical vapour deposition, ALCVD, oratomic layer epitaxy, ALE, is a thin-film-deposition technique thatrelies on alternating self-terminating gas-to-surface reactions. Thefilm is formed by sequential pulsing of two or more reactants, usingpurging with inert gas between the precursor pulses to avoid gas-phasereactions. Operated under ideal conditions this process ensuressaturation of all surfaces with precursor for each applied precursorpulse. The growth of the film will therefore depend on the saturationdensity of the involved precursor during a pulse. Unlike most otherdeposition and crystal growth techniques the growth is in the ideal casenot dependent on the distribution of the precursors or rate of formationof growth steps on the crystallites forming the film. The growth thusfollows a somewhat different type of dynamics and ensures even growth onall exposed surfaces for each pulse.

BACKGROUND ART

There are a large number of patent applications describing variousaspects of thin film Li-deposition; however the majority pertain todifferent deposition methods such as pulsed laser deposition,sputtering, and the like. These methods present different issues towhich solutions must be found, for instance laser deposition andsputtering may be harmful to the substrate due to the high energy impactof the deposited method upon the substrate. Furthermore these methodsare difficult to control in an adequate manner and in such applicationswherein layer thickness control is of vital importance the methods mayprove difficult to apply. There is additionally the difficulty ofproviding a defect free or pinhole free layer which is desired in manyindustrial applications. Such applications may be as an electronicbarrier between other materials or layers so that there is no electricleakage across the barrier or in some applications no physical contactbetween layers whom one desires to separate. By sputtering or by laserdeposition techniques it is very difficult to ensure that the entiresurface is covered and a defective film may result. An area wherein itis especially important to provide defect free layers is in batterytechnology wherein lithium-comprising layers are to be separated byelectrolytes allowing for the passage of lithium ions, but wherein nophysical or electric contact should be made between the layers to avoidan irreversible reduction in the battery efficiency. The layers shouldpreferably be as thin as possible to provide the least resistance to thepassage of the ions, and thus layer control is of the utmost importance.

P. Fragnaul et al. in J. Power Sources 54.362 1995 proposes a CVD methodfor the deposition of thin films of the active cathode materials LiCoO₂and LiMn₂O₄ by chemical techniques. Low pressure chemical vapourdeposition is described as being successful at readily preparing LiCoO₂at temperatures ranging from 450 to 650° C.; however, in order toprepare the spinel phase LiMn₂O₄, temperatures greater than 600° C. wererequired. No mention is made of the use of ALD or ALE technology.

WO00/25378 to Menachem et al. describes a method for forming a batteryin which CVD techniques are used to form an electrolyte barrier in aLi-solid state battery. However, CVD differs widely from ALD in that CVDand MOCVD are not self-limiting reactions as is ALD, and they are thusmore difficult to control. There are also issues in that the reactiontemperature must be very closely monitored, and in that there mightoccur undesirable side reactions whilst performing the deposition. Incontrast ALD proposes a simple self-limiting reaction wherein amonolayer of the desired compound may be deposited on a substrate, andwherein each layer formation reaction is self controlled.

US20070026309 to Notten et al. describes a method for forming a solidbattery wherein the anode and cathode are separated by an electrolyte.There is a description of the electrolyte layer being a lithiumcomprising electrolyte wherein said lithium comprising electrolyte isdeposited by either Physical Vapor Deposition (PVD), Chemical VaporDeposition (CVD), and/or Atomic Vapor Deposition (AVD). However there isno mention of how this is to be performed, and the sequential listing ofalternative methods for the production of said electrolyte is merely alisting of known gas phase deposition methods. No mention has been foundof the authors citing an ALD methodology as described in the presentinvention elsewhere in the art. On the contrary the authors themselveshave in WO2006092747 solely proposed the use of MOCVD in the productionof the Li layers, this being a clear indication that the inventors havein fact not used ALD methodology to produce the Li layers. If theauthors had proposed the use of ALD in the production of Li comprisinglayers, they would as persons skilled in the art have recognised thebeneficial aspects of the method as such, and would have proposed usingALD instead of MOCVD. EP06710932/WO2006056963 to the same authors arevariations on the same theme of the above invention.

U.S. Pat. No. 6,818,517 describe the use ofALD technique to for metaloxide layer and list a considerable number of metals. There is noexample which discloses how deposition of Li or La can be accomplished.

US2004/0043149 disclose the deposition of metal silicates or phosphatesusing CVD and ALD.

SHORT SUMMARY OF THE INVENTION

The hereinafter described invention seeks to overcome at least some ofthe shortcomings of the background art and comprises a method forformation of a Li-comprising layer on a substrate by atomic layerdeposition comprising the following steps:

a) providing a substrate in a reaction chamber wherein said reactionchamber is arranged for gas-to-surface reactions,

b) pulsing a lithium precursor through said reaction chamber,

c) reacting said lithium precursor with at least one surface of saidsubstrate,

d) purging of said reaction chamber

d1) by sending a purge gas through said reaction chamber for the purgingof the reaction chamber or

d2) by evacuating said chamber, and

e) repeating steps b) to d) a desired number of times in order for theformation of a thin film layer of a lithium comprising material uponsaid at least one surface of said substrate.

Further advantageous embodiments of the invention are described in thehereinafter enclosed dependant claims.

In one embodiment of the method according to the present invention eachstep of the process is independently repeated a desired number of times.

In another embodiment of the method according to the present inventionthe steps b) through d) are repeated with independently chosen lithiumprecursors in step b).

In one aspect, the present invention provides a method wherein furtherto the described steps, a lanthanum and titanium comprising precursor ispulsed through the reaction chamber such that the reaction resultingsequence comprises:

-   -   a) providing a substrate in a reaction chamber wherein said        reaction chamber is arranged for gas-to-surface reactions,    -   b) pulsing a lanthanum precursor through said reaction chamber,    -   c) reacting said lanthanum precursor with said at least one        surface of said substrate,    -   d) purging of said reaction chamber        -   d1) by sending a purge gas through said reaction chamber for            the purging of the reaction chamber or        -   d2) by evacuating said chamber,    -   e) pulsing an oxygen precursor through said reaction chamber,    -   f) reacting said oxygen precursor with said at least one surface        of said substrate,    -   g) purging of said reaction chamber        -   g1) by sending a purge gas through said reaction chamber for            the purging of the reaction chamber or        -   g2) by evacuating said chamber,    -   h) pulsing a lithium precursor through said reaction chamber,    -   i) reacting said lithium precursor with a surface layer of the        substrate,    -   j) purging of said reaction chamber        -   j1) by sending a purge gas through said reaction chamber for            the purging of the reaction chamber or        -   j2) by evacuating said chamber,    -   k) pulsing an oxygen precursor through said reaction chamber,    -   l) reacting said oxygen precursor with said at least one surface        of said substrate,    -   m) purging of said reaction chamber        -   m1) by sending a purge gas through said reaction chamber for            the purging of the reaction chamber or        -   m2) by evacuating said chamber,    -   n) pulsing a titanium precursor through said reaction chamber,    -   o) reacting said titanium precursor with said at least one        surface of said substrate,    -   p) purging of said reaction chamber        -   p1) by sending a purge gas through said reaction chamber for            the purging of the reaction chamber,        -   p2) or by evacuating said chamber,    -   q) pulsing an oxygen precursor through said reaction chamber,    -   r) reacting said oxygen precursor with said at least one surface        of said substrate,    -   s) purging of said reaction chamber        -   s1) by sending a purge gas through said reaction chamber for            the purging of the reaction chamber,        -   s2) or by evacuating said chamber,    -   t) repeating steps b) to s) a desired number of times in order        for the formation of a thin film layer of a lithium, lanthanum        and titanium comprising material upon said at least one surface        of said substrate.

In one embodiment of the method according to the present invention eachstep of the process is independently repeated a desired number of times.In yet another embodiment is the groups of steps b) to g), h) to m)and/or n) to s) can each independently be repeated a desired number oftimes before continuing with the rest of the steps.

In another aspect the present invention provides a method which mayresult in an electrolyte comprising no or a limited number of pin holes.When applied in batteries this method will provide a lower efficiencylos over time.

In yet another aspect the invention may provide improved sensormaterials for sensors for measuring the concentration of alkali ions inliquids.

In another aspect the invention may provide improved LiNbO₃ thin films.Due to its unique electro-optical, photoelastic, piezoelectric andnon-linear properties Lithium Niobate is widely used in a variety ofintegrated and active acousto-optical devices.

The invention may also provide improved Lithium Tantalate which exhibitsunique electro-optical, pyroelectric and piezoelectric propertiescombined with good mechanical and chemical stability and, widetransparency range and high optical damage threshold. This makes LiTaO₃well-suited for numerous applications including electro-opticalmodulators, pyroelectric detectors, optical waveguide and SAWsubstrates, piezoelectric transducers etc.

The figures are solely intended for illustration purposes and should notbe construed in any manner limiting the invention:

FIG. 1 is a representation of the Li₂CO₃ deposition rate as a functionof deposition temperature for an embodiment of the invention.

FIG. 2 is a representation of growth rate as a function of pulsing ratioof precursor cycles, compared to the deposition rates of binaryprocesses according to an embodiment of the invention. There is analternating deposition of Li and La compounds.

FIG. 3 is a representation of the compositional change of Li—Lacontaining films as a function of pulsing ratio of each of the Li and Laprecursors according to an embodiment of the invention.

FIG. 4 Average growth per cycle of the LLT films as a function of theLi(t-OBu) pulse time.

EMBODIMENTS OF THE INVENTION

The present invention will hereinafter be described with reference tothe enclosed figures, tables and examples. Although specific methodshave been provided as examples of embodiments of the invention, it willbe clear to a person skilled in the art that variants of the inventionare within the scope of the invention.

The present invention discloses a method for the production oflithium-comprising thin film layers by Atomic layer deposition(hereafter ALD) wherein a substrate is to be provided by a thinpreferably defect free layer of a lithium comprising compound. Themethod comprises pulsing of a lithium precursor into a reaction chamberwherein is arranged a substrate which is to be furnished with a lithiumcomprising layer. If required, an inert purge gas is pulsed through thereaction chamber after each pulse of lithium comprising precursor, orafter each sequence of lithium precursor pulses, or even concurrentlywith the precursor. Alternatively several purge pulses may be performedbetween each lithium precursor pulse. In some instances purging thechamber may be performed simply by evacuating the chamber. With eachlithium precursor pulse cycle, a layer of lithium-containing materialwill be deposited upon the substrate such that in a layer by layerfashion the lithium-containing material will be deposited upon thesubstrate surface according to the ALD principle.

The main and surprising effect of the invention is that it has provenpossible to deposit a lithium layer on a substrate using ALD in spite ofthe fact that lithium and other alkali metals are provided with a singleligand in gaseous phase for reaction. It has heretofore been thoughtthat alkali metals would not be suitable for ALD methods as the ligandon the Li-precursor would undergo reactions with the active sites on thesurface and form part of a volatile specie and not take part in a selfhindering mechanism. In this way the surface would be terminated byLi-atoms who are significantly smaller than their anionic counterpartsand easily be adsorbed into the film and not be able to produce asuitable terminating layer to prevent further reactions on the anioniccounterparts of the film surface. This has now empirically been provento be wrong, which is surprising and contravenes a prejudice of the art.

Accordingly the present invention provides a new method for applying athin film comprising an alkali metal on a surface by use of the ALDtechnique.

In order for activation of the surface between each deposition cycle itmay in an embodiment of the invention be necessary to includeintroducing an oxygen precursor in the cycle to incorporate oxygenmoieties on the surface after each deposition. Any suitable oxygenprecursor such as for instance water, O₃ or any other oxygen comprisinggaseous compound may serve the purpose as will be evident to a personskilled in the art. This oxygen containing precursor is often referredto as the oxidizer in the literature, even though there may be no clearredox reaction taking part in the main formation of the film. The oxygenprecursor may be pulsed into the reaction chamber in a manner resemblingthat of the pulsing of the precursor material. An illustration of therate of deposition of Li per deposition cycle according to an embodimentof the invention upon a substrate with interceding oxidisation by O₃ isgiven in FIG. 1. The deposition is temperature dependent, withdeposition at higher temperatures being less effective than at lowertemperatures. Although it is preferable to first pulse the metal phasethrough the reaction chamber for deposition upon the substrate, it mayin some instances be preferable to pulse said oxygen comprisingprecursor prior to pulsing the metal comprising precursor through thechamber. The precise manner of pulsing may vary, as ALD methods, andvariants thereupon, as such are known.

In one embodiment of the present invention the method and obtained thinfilm are characterised by comprising Li in the form of lithium oxide, asa single oxide or together with one or more other metals or metal oxidesforming a metal(s)—Li-oxide thin film or together with carbon forminglithium carbonate. Where the thin film may have a layered structure.

The deposition temperature should be adjusted such that the depositionoccurs at the best possible rate, however, as is evident, thetemperature must not be too high such that the substrate is damaged, orthe precursor decomposes noticeable. FIG. 1 illustrates use of Li(thd)(lithium 2,2,6,6-tetramethylheptane-3,5-dionate) as a lithium precursor.Li(thd) is stable to about 400° C. which thus for this precursor definesthe highest possible deposition temperature. Using other precursors,higher or lower deposition temperatures may be envisaged, depending onthe physico-chemical properties of the precursor and the substrate.Amongst other possible precursors are found organometallic compoundssuch as lithium alkoxides i.e. Li(t-BuO) (lithium tert-butoxide), alkylsi.e. BuLi (n-butyl lithium), cyclic lithium compounds i.e. LiCp (lithiumcyclopentadienyl), lithium dicyclohexylamid, and bimetallic ormultimetallic compounds such as (M,Li)R compounds, where M may beanother metal from the periodic table, where R may be one or moreorganic fragments and where both M and Li may be incorporated into thefilm. The stoichiometry of the M and Li may vary depending on theselection or organic compounds, this last group of precursors mayinclude compounds such as (Ti, Li)-, (La, Li)- and (Ti, La, Li)-organiccompounds. This evidently encompasses a large number of possibleprecursors that may be used, wherein each may be chosen for the specificuse on a specific substrate or chosen due to economic, environmental orother considerations. The invention is not limited to a singleprecursor, and the use of a plurality of different precursors may beenvisaged.

A separate consideration concerns the specific pulsing scheme to be usedfor pertaining to the duration of each pulse and to the pulse sequence.Each pulse sequence may be varied according to need, however the pulseduration of each precursor should be such that the there is sufficienttime for the entire substrate surface to have reacted with theprecursor. Typical precursor pulse durations may range from about 0.1 toabout 20 seconds, preferably from about 0.1 to about 2 second, oftenabout 0.8 seconds. In a similar manner, the purge pulse durations shouldalso be tailored to ensure that the purge has been effective. Typicalpurge pulse durations may range from about 0.8 to about 3 seconds orlonger even up to 6-12 seconds, but often the purge pulse will have aduration of 1-2 seconds. Purge pulse durations may vary significantlydepending upon which precursor has been used, and whether the purgingpulse occurs after a possible oxidising pulse as described above. Thepulse and purge times depends mostly on the fluid dynamics of thedeposition system and the chosen temperature of the precursor, i.e. itsvapour pressure. A purge of the reaction chamber may be carried out inseveral different ways. The main importance of the purge is to avoidthat there are undesirable gas phase reactions between different typesof precursors. A purge may consist of an additional pulse of an inertgas capable of removing excess and unreacted precursors from theprevious pulse. A purge may alternatively be carried out by evacuatingthe chamber by reducing the pressure and in this way remove excess andunreacted precursor from the previous pulse. Alternatively the purge maybe effectuated by using the flushing effect of a carrier gas directingthe precursor to the substrate and carrying away any by-products. Thecarrier gas may be used in a pulsevise or continuous manner. Somereactions may occur with a minimum of physisorption of excess precursorto the substrate so that a purging period may be virtually absent. Thesame considerations with respect to the purging pulse durations arerelevant to the duration of the oxidising pulse (oxygen containingprecursor), which may range from about 0.1 to about 2 seconds,preferably from about 0.5 to about 1 second, often about 1.2 secondsdepending on the oxidiser. As is evident, shorter or longer pulses ofeach specific compound may prove necessary depending on the surfacereaction kinetics as will be evident to a person skilled in the art.

An example of a possible pulsing sequence may thus be:

-   -   0.8 s/1.2 s/1.5 s/2.0 s        Metal-precursor/purge/oxygen-precursor/purge.

Using these pulses in an embodiment of the invention one achieves alayer composition as described in table as measured by a TOF-ERDA (timeof flight elastic recoil detection analysis) method.

TABLE 1 Layer composition in atomic percent for an example of anembodiment of the invention Deposition temperature Li O C H Na F 185° C.33 49 17 0.22 0.33 0.25 225° C. 33 48 18 0.2  0.21 0.29

Using Li(thd) as the metal precursor and O₃ as the oxidiser this resultsin the deposition rate as shown in FIG. 1. The pulsing sequence isrepeated as many times as is necessary in order to form the desiredlayer thickness. The layer thickness may be measured by any appropriatemethod or estimated based on empirical data.

A main purpose of the invention as such is to produce an electrolytelayer suitable for use in lithium battery applications. As such it hasbeen considered advantageous to provide an electrolyte layer comprisingfurther to said lithium layer a lanthanum comprising layer. Thus in anembodiment of the invention, further to the pulses of lithium comprisingprecursor a lanthanum comprising precursor is pulsed through thereaction chamber for reaction and subsequent deposition upon thesubstrate.

Lithium as such has long been of major interest in the development ofthin film batteries, in particular with respect to its use as an anode,due to its very high energy density of about 3,800 mAh/g and to its veryhigh conductivity. However the reactive nature of Li has necessitatedthe use of large amounts of excess lithium due to that Li typicallyreacts with the electrolyte resulting in reaction losses. Previousefforts have been concentrated upon the use of Lipon (lithium phopherousoxynitride) electrolytes, however Li—La-M-O systems, where M is a metal,may present much higher lithium conductivities and would as such provemore effective than the previously studied Lipon electrolytes.

Accordingly an object of the invention is to provide an electrolytecomprising a desired proportion of Li and La compounds using ALDmethodology. This will result in a method according to the inventionwhereby the Li precursor and La precursor will be furnished to thereaction chamber in a predetermined sequence such that the desiredcomposition of the layer is achieved. The specific composition maydepend on which use is intended for the electrolyte as will be evidentto a person skilled in the art. As for the other compounds to bedeposited upon the substrate, the pulse lengths may vary and depend uponthe reaction kinetics on the surface. The La precursor pulse durationmay typically vary between 0.5 to about two seconds, preferably about0.8-1.5 seconds. An example of a deposition cycle may thus be:

-   -   0.8-1.5 s/1.2 s/1.5 s/2.0 s Li(thd)/purge/oxygen precursor/purge    -   0.8-1.5 s/1.2 s/1.5 s/2.0 s La(thd)₃/purge/oxygen        precursor/purge

Any suitable La precursor may serve as is evident to a person skilled inthe art, in one embodiment of the invention the La precursor is ametal-organic La-compound. In this example use is made of a La(thd)₃precursor.

FIG. 2 shows an illustration of the variation of the growth rate of theresulting deposited layer with respect to the percentage of Li(thd)/O₃cycles. FIG. 3 correspondingly illustrates relative amount of Lideposited upon the substrate with respect to the percentage ofLi(thd)/O₃ cycles.

Using a TOF-ERDA measurement, it has empirically been found that thecomposition of the layer of each compound varies according to table 2 inthis embodiment of the invention.

TABLE 2 Layer composition for an example of an embodiment of theinvention % Li Li/La pulses La Li ratio O C H Na F 16.7 20  3 11.1 61 141.4 <0.1 0.4  50 15  9 36.7 58 17 1.5 0.1 0.25 75  7 22 75.9 54 16 0.60.8 0.4  90.9  2 30 94 50 17.5 0.3 0.5 0.33

In one embodiment of the present invention includes furtherincorporating Ti into the structure thereby obtaining a Li—La—Ti—Olayered compound. Ti can be included by a process similar to the Laprocess described above but applying for instance TiCl₄ as a precursorand II₂O as oxygen comprising precursor. Applicable Ti precursorsinclude for instance halogenides of Ti, Ti—Li- and Ti-organometallic ormetalorganic compounds. An example of a deposition cycle may thus be:

-   -   8 s/2 s/2 s/2.0 s Li(t-OBu)/purge/oxygen precursor/purge    -   2 s/2 s/6 s/3.0 s La(thd)₃/purge/oxygen precursor/purge    -   0.5 s/1 s/2 s/2.0 s TiCl₄/purge/oxygen precursor (H₂O)/purge

This is illustrated in the following example.

Thin films have been deposited using a F-120 Sat (ASM Mirochemistry)reactor by using La(thd)₃ (thd=2,2,6,6-tetramethyl-3,5-heptanedione,made in house according to the procedure described in [G. S. Hammond, D.C. Nonhebel, and C.-H. S. Wu, Inorg. Chem., 2 (1963) 73-76]), TiCl₄(>99.0%, Fluka), and Li(t-OBu) (t-OBu=Lithium tert-butoxide) as metalprecursors and H₂O (distilled) or ozone as oxygen precursors. The H₂Oand TiCl₄ precursors were kept at room temperature in containers outsideof the reactor during the depositions. The La(thd)₃ and Li(t-OBu) wassublimed at 185° C. and 160° C., respectively, and dosed into thereaction chamber using inert gas valves. All films were deposited onsingle crystalline substrates of Si(111) and soda lime glass substratesat a reactor temperature of 225° C.

Nitrogen was produced in house using a Schmidlin Nitrox 3001 generator(99.999% as to N2+Ar) and used as purging and carrier gas. The pressureof the reactor during growth was maintained at ca. 2 mbar by employingan inert gas flow of 300 cm³ min⁻¹. Ozone was produced by feeding99.999% O₂ (AGA) into an OT-020 ozone generator from OzoneTechnology,providing an ozone concentration of 15 vol % according tospecifications. An ozone flow of ca. 500 cm³ min⁻¹ was used during theozone pulses.

Thin films in the La—Li—Ti—O system were deposited using an intimatemixture of the cycles used for depositing the different binary oxides.These will be referred to as subcycles. The pulse and purge parametersfor deposition of the different elements are given in the table 3 below:

TABLE 3 Puls and purge parameters for an example of an embodiment of theinvention Element Pulse/s Purge/s H₂O/O₃ pulse/s Purge/s Ti 0.5 1 2(H₂O) 2 La 2 2 6 (O₃)   3 Li 8 2 2 (H₂O) 2

The sub-cycles were combined in different ratios and order to controlthe stoichiometry of the deposit the Lithium-lanthanum-titanium-oxides(LLT).

The pulsing order of the sub-cycles was shown to have an effect on thefilm growth, and a self-limiting mechanism was found when pulsing theLi-compound after the La-compound and not after the Ti-compound. ALDtype of growth of lanthanum oxide and titanium oxide usingLa(thd)₃+ozone and TiCl₄+H₂O has been described in [M. Nieminen, T.Sajavaara, E. Rauhala, M. Putkonen, and L. Niinistö, J. Mater. Chem., 11(2001) 2340-2345.] and [J. Aarik et al., J. Cryst. Growth 148: 268(1995), or J. Aarik, A. Aidla, V. Sammelselg, H. Siimon, T. Uustare, J.Cryst. Crowth 169 (1996) 496], respectively. The effect of Li(t-OBu)pulse time on the average growth per cycle of the films grown using apulsing scheme of sub-cycles as: 400×(1×Ti+3×La+1×Li) is shown in FIG.4. FIG. 4 depictures the average growth per cycle of the LIT films as afunction of the Li(t-OBu) pulse time. The growth rate stabilized at ca.0.048 nm/cycle for films deposited using at least 8 s pulse ofLi(t-OBu).

The composition of the films was analyzed by TOF-ERDA (Time-of-FlightEnergy Recoil Detection Analysis) and stabilized at ca.Li_(0.34)La_(0.30)TiO_(2.9) for films deposited with more than 8 s ofLi(t-OBu) pulse. In addition to these elements the films contained somechlorine (3.0-3.7 at. %) carbon (1.9-3.0 at. %) and hydrogen (0.7-2.5at. %) as impurities. Analysis performed by Leila Costelle, Departmentof Physics, University of Helsinki, Finland.

Equivalent to this process other metal organic, organo metallic, orhalogenides may be included in the Li comprising film.

It is thus to a large degree possible to design the electrolyteaccording to the needs of the task. Amongst possible uses for thiselectrolyte are as a thin-film barrier between Li layers in a thin-filmbattery, and it is one of the objects of the present invention toprovide such an electrolyte. Although battery technology is one of thepossible uses of the present method, it should be clear that otherpossible uses of the ALD method for depositing Li-layers on a substrateare foreseen. Although exemplified above for use in a battery this willnot be the only application for the present invention.

The present invention has thus proposed a method for the formation ofthin Li-comprising layers on a substrate using an ALD-method.

While embodiments of the invention have been described, it is understoodthat various modifications to the disclosed process and itsimplementation may be made without departing from the scope of theinvention as define by the subsequent claims.

The invention claimed is:
 1. A method for formation of a Li-comprisinglayer on a substrate by atomic layer deposition comprising the followingsteps: a) providing a substrate in a reaction chamber wherein saidreaction chamber is arranged for gas-to-surface reactions, b) pulsing alithium precursor through said reaction chamber, c) reacting saidlithium precursor with at least one surface of said substrate, d)purging of said reaction chamber d1) by sending a purge gas through saidreaction chamber for the purging of the reaction chamber or d2) byevacuating said chamber, and repeating steps b) to d) a desired numberof times in order for the formation of a thin film layer of a lithiumcomprising material upon said at least one surface of said substrate,wherein the lithium precursor is selected from among lithium2,2,6,6-tetramethylheptane-3,5-dionate, lithium alkoxides, lithiumalkyls, cyclic lithium compounds, lithium dicyclohexamide, andbimetallic or multimetallic compounds.
 2. A method according to claim 1wherein steps b) through d) are repeated with independently chosenlithium precursors in step b).
 3. A method according to claim 1, furthercomprising the following steps: e) pulsing an oxygen precursor throughsaid reaction chamber, f) reacting said oxygen precursor with said atleast one surface of said substrate, g) purging of said reactionchamber, where the purging of said chamber may be performed by sending apurge gas through said reaction chamber for the purging of the reactionchamber or by evacuating said chamber, repeating steps b) to g) adesired number of times in order for the formation of a thin film layerof a lithium comprising material upon said at least one surface of saidsubstrate.
 4. A method for formation of a Li-comprising layer on asubstrate by atomic layer deposition comprising the following steps: a)providing a substrate in a reaction chamber wherein said reactionchamber is arranged for gas-to-surface reactions, b) pulsing a lanthanumprecursor through said reaction chamber, c) reacting said lanthanumprecursor with said at least one surface of said substrate, d) purgingof said reaction chamber, e) pulsing an oxygen precursor through saidreaction chamber, f) reacting said oxygen precursor with said at leastone surface of said substrate, g) purging of said reaction chamber, h)pulsing a lithium precursor through said reaction chamber, i) reactingsaid lithium precursor with a surface layer of the substrate, j) purgingof said reaction chamber, k) pulsing an oxygen precursor through saidreaction chamber, l) reacting said oxygen precursor with said at leastone surface of said substrate, m) purging of said reaction chamber, n)repeating steps b) to m) a desired number of times in order for theformation of a thin film layer of a lithium and lanthanum comprisingmaterial upon said at least one surface of said substrate, where thepurging of said chamber may be performed by sending a purge gas throughsaid reaction chamber for the purging of the reaction chamber or byevacuating said chamber.
 5. A method for formation of a Li-comprisinglayer on a substrate by atomic layer deposition comprising the followingsteps: a) providing a substrate in a reaction chamber wherein saidreaction chamber is arranged for gas-to-surface reactions, b) pulsing alanthanum precursor through said reaction chamber, c) reacting saidlanthanum precursor with said at least one surface of said substrate, d)purging of said reaction chamber, e) pulsing an oxygen precursor throughsaid reaction chamber, f) reacting said oxygen precursor with said atleast one surface of said substrate, g) purging of said reactionchamber, h) pulsing a lithium precursor through said reaction chamber,i) reacting said lithium precursor with a surface layer of thesubstrate, j) purging of said reaction chamber, k) pulsing an oxygenprecursor through said reaction chamber, l) reacting said oxygenprecursor with said at least one surface of said substrate, m) purgingof said reaction chamber, n) pulsing a titanium precursor through saidreaction chamber, o) reacting said titanium precursor with said at leastone surface of said substrate, p) purging of said reaction chamber, q)pulsing an oxygen precursor through said reaction chamber, r) reactingsaid oxygen precursor with said at least one surface of said substrate,s) purging of said reaction chamber, t) repeating steps b) to s) adesired number of times in order for the formation of a thin film layerof a lithium, lanthanum and titanium comprising material upon said atleast one surface of said substrate, where the purging of said chambermay be performed by sending a purge gas through said reaction chamberfor the purging of the reaction chamber or by evacuating said chamber.6. A method according to claim 1, wherein each step of the process isindependently repeated a desired number of times.
 7. A method accordingto claim 3, where the steps b)-g) are independently repeated one or moretimes before continuing the sequence.
 8. A method according to claim 1,where the thin film layer is an oxide or a carbonate layer or a mixturethereof.
 9. A method according to claim 5 for the production of aLa—Li—Ti—O layered thin film.
 10. A method according to claim 1 for theproduction of a lithium-comprising thin film battery.
 11. A methodaccording to claim 1 for the production of a lithium-comprisingelectrolyte thin film for use in a battery.
 12. A method according toclaim 4, wherein the lithium precursor is selected from among lithium2,2,6,6-tetramethylheptane-3,5-dionate, lithium alkoxides, lithiumalkyls, cyclic lithium compounds, lithium dicyclohexamide, andbimetallic or multimetallic compounds.
 13. A method according to claim12, wherein each step of the process is independently repeated a desirednumber of times.
 14. A method according to claim 12, where the groups ofsteps b)-g) and f)-m) respectively are independently repeated one ormore times before continuing the sequence.
 15. A method according toclaim 12, where the thin film layer is an oxide or a carbonate layer ora mixture thereof.
 16. A method according to claim 12 for the productionof a lithium-comprising thin film battery.
 17. A method according toclaim 12 for the production of a lithium-comprising electrolyte thinfilm for use in a battery.
 18. A method according to claim 5, whereinthe lithium precursor is selected from among lithium2,2,6,6-tetramethylheptane-3,5-dionate, lithium alkoxides, lithiumalkyls, cyclic lithium compounds, lithium dicyclohexamide, andbimetallic or multimetallic compounds.
 19. A method according to claim18, wherein each step of the process is independently repeated a desirednumber of times.
 20. A method according to claim 18, where the groups ofsteps b)-g), f)-m) and n)-s) respectively are independently repeated oneor more times before continuing the sequence.
 21. A method according toclaim 18, where the thin film layer is an oxide or a carbonate layer ora mixture thereof.
 22. A method according to claim 18 for the productionof a lithium-comprising thin film battery.
 23. A method according toclaim 18 for the production of a lithium-comprising electrolyte thinfilm for use in a battery.
 24. A battery, comprising an electrolyte orelectrode material coated with a thin film layer having a thickness of19.2 nanometers (nm) or less, wherein the thin film layer compriseslithium, and monolayers of a metal oxide or monolayers of a metalcarbonate.
 25. The battery of claim 24, wherein the thin film layer isproduced using a process that comprises Atomic Layer Deposition.
 26. Thebattery of claim 24, wherein the thin film layer comprises an anodematerial.
 27. The battery of claim 24, wherein the thin film layercomprises one or more elements from the periodic table.
 28. The batteryof claim 24, wherein the thin film layer comprises Titanium, Lanthanum,Niobium or Tantalum.
 29. The battery of claim 24, wherein the thin filmlayer comprises one or more lithium metal(s) oxide selected from:lithium titanate, lithium lanthanate, lithium niobate, lithiumtantalate, and lithium lanthanum titanate.
 30. The battery of claim 24,wherein the lithium is adsorbed into the thin film layer from a lithiumprecursor.
 31. A battery, comprising an electrolyte or electrodematerial coated with a thickness-controlled lithium niobium oxide layerhaving a thickness of 19.2 nanometers (nm) or less.
 32. The battery ofclaim 31, wherein the thickness-controlled lithium niobium oxide layercomprises one or more elements from the periodic table.
 33. The batteryof claim 31, wherein the thickness-controlled lithium niobium oxidelayer comprises Titanium, Lanthanum or Tantalum.
 34. The battery ofclaim 31, wherein the lithium niobium oxide layer is produced using aprocess that comprises Atomic Layer Deposition.
 35. A battery,comprising an electrolyte or electrode material coated with athickness-controlled thin film layer having a thickness of 19.2nanometers (nm) or less using an atomic layer deposition process,wherein the thin film layer comprises monolayers of a metal oxide ormonolayers of a metal carbonate.
 36. The battery of claim 35, whereinthe thin film layer comprises an anode material.
 37. The battery ofclaim 35, wherein the thin film layer further comprises one or moreelements from the periodic table.
 38. The battery of claim 35, whereinthe thin film layer comprises Titanium, Lanthanum, Niobium or Tantalum.39. The battery of claim 35, wherein the thin film layer comprises oneor more lithium metal(s) oxide selected from: lithium titanate, lithiumlanthanate, lithium niobate, lithium tantalate, and lithium lanthanumtitanate.
 40. The battery of claim 35, wherein the lithium is adsorbedinto the thin film layer from a lithium precursor.